/*
 * Copyright (c) The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

import { type CharStream } from "./CharStream.js";
import { type Token } from "./Token.js";
import { type TokenFactory } from "./TokenFactory.js";

/**
 * A source of tokens must provide a sequence of tokens via {@link nextToken()}
 * and also must reveal it's source of characters; {@link CommonToken}'s text is
 * computed from a {@link CharStream}; it only store indices into the char
 * stream.
 *
 * Errors from the lexer are never passed to the parser. Either you want to keep
 * going or you do not upon token recognition error. If you do not want to
 * continue lexing then you do not want to continue parsing. Just throw an
 * exception not under {@link RecognitionException} and Java will naturally toss
 * you all the way out of the recognizers. If you want to continue lexing then
 * you should not throw an exception to the parser--it has already requested a
 * token. Keep lexing until you get a valid one. Just report errors and keep
 * going, looking for a valid token.
 */
export interface TokenSource {
    /**
     * Return a {@link Token} object from your input stream (usually a
     * {@link CharStream}). Do not fail/return upon lexing error; keep chewing
     * on the characters until you get a good one; errors are not passed through
     * to the parser.
     */
    nextToken(): Token;

    /**
     * Get the line number for the current position in the input stream. The
     * first line in the input is line 1.
     *
      @returns The line number for the current position in the input stream, or
     * 0 if the current token source does not track line numbers.
     */
    line: number;

    /**
     * Get the index into the current line for the current position in the input
     * stream. The first character on a line has position 0.
     *
      @returns The line number for the current position in the input stream, or
     * -1 if the current token source does not track character positions.
     */
    column: number;

    /**
     * Get the {@link CharStream} from which this token source is currently
     * providing tokens.
     *
      @returns The {@link CharStream} associated with the current position in
     * the input, or `null` if no input stream is available for the token
     * source.
     */
    inputStream: CharStream | null;

    /**
     * Gets the name of the underlying input source. This method returns a
     * non-null, non-empty string. If such a name is not known, this method
     * returns {@link IntStream.UNKNOWN_SOURCE_NAME}.
     */
    sourceName: string;

    /**
     * Set the {@link TokenFactory} this token source should use for creating
     * {@link Token} objects from the input.
     *
     * @param factory The {@link TokenFactory} to use for creating tokens.
     */
    set tokenFactory(factory: TokenFactory<Token>);

    /**
     * Gets the {@link TokenFactory} this token source is currently using for
     * creating {@link Token} objects from the input.
     *
      @returns The {@link TokenFactory} currently used by this token source.
     */
    get tokenFactory(): TokenFactory<Token>;
}
